High tension igniter plugs

ABSTRACT

AN IGNITER PLUG COMPRISING INNER AND OUTER ELECTRODES DEFINING THEREBETWEEN AN ANNULAR PASSAGE ENDING IN AN ANNULAR GAP FOR DEVELOPMENT OF IGNITION SPARKS. A GAS IS FED TO THE PASSAGE FOR EMERGENCE THROUGH THE GAP. A WHIRLING MOTION IS IMPARTED TO THE GAS IN THE PASSAGE TO GIVE THE SPARKS A LIKE WHIRLING MOVEMENT. ALTERNATIVELY OR ADDITIONALLY, THE OPERATIVE END PORTION OF THE INNER ELECTRODE FORMS ARE OUTWARDLY FLARING DEFLECTOR FOR THE FLOW OF GAS TO PROMOTE THE FORMATION OF AN IGNITION FLAME.

Jan'. 26,1971'1 L. J. BAUGER ETAL 5 3,558,251

, H HIGH TENSION IGNITER PLUGS Filed Feb; 24, 1969 4 Sheets-Sheet 1 FIG.7a

Jan. 26, 1971 J. BAUGER ETAL 3,558,251

- HIGH TENSION IGNITER PLUGS Filed Feb. 24, 1969 4 Sheets-Sheet 2 wal QJMMQIUJ (Oil Jan) CEHWU 155251971 L, ,BAUG.L; ETAL 3,558,251

HIGH TENSION IGNITER PLUGS v Filed Feb. 24, 1959 r 4 sheet -shat 5 mwamwL. J. BAUGER ETAL 3,558,251

HIGH TENSION IGNITER PLUGS 4 Sheets-Sheet 4 Filed Feb. 24, 1969 O 1X1 ilUnited States Patent 3,558,251 HIGH TENSION IGNITER PLUGS Louis JulesBauger, Vanves, Roland Robert Charles Beyler, Levallois-Perret, AdolpheRobert Lefebvre, La Rochette, Herve Alain Quillevere,Issy-les-Moulineaux, and Michel Bernard Schenher, Paris, France,assignors to Societe Nationale dEtude et de Construction de MoteursdAviation, Paris, France Filed Feb. 24, 1969, Ser. No. 801,546 Claimspriority, application France, Feb. 27, 1968,

Int. Cl. l zs 3/00 US. Cl. 431-266 7 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to a high tension igniter plug for igniting afuel mixture, for example an air/fuel mixture in the combustion chamberof a jet engine.

{High tension igniter plugs produce sparks between determinate points ontwo electrodes. Conventionally, such igniter plugs have an inner orcentral electrode and an outer or earth electrode in the form 'of acylindrical element connected to earth and surrounding the centralelectrode, said cylindrical electrode carrying at its operativeextremity one or more tips directed towards the inner electrode, thespark arcs being struck between the inner electrode and the nearestpoint or points of said tip or tips.

It is an object of the invention to provide a high tension igniter plugof improved operating efiiciency, in particular a plug capable ofproviding faster ignition.

The high tension igniter plug according to one feature of the inventioncomprises an inner electrode, an outer electrode surrounding the innerelectrode to define an annular passage therebetween, said electrodeshaving operative extremities relatively positioned for development ofignition sparks or arcs therebetween during use, and means for impartinga whirling or gyratory motion to a gas or gas/ vapour mixture which inuse is fed to the annular passage for emergence through the annular gapbetween the operative extremities of the electrodes.

Thus, we have discovered that, if the aforementioned tips on the outerelectrode are removed, and if a substantial flow of air or of some othergas is created between the inner electrode and the outer electrode, thearc struck between the operative extremities of the electrodes splitsinto several individual sparks distributed more or less uniformly aroundthe annular gap between the electrode extremities. Moreover, the gasstream tends to project the ionised arcing zone downstream and thusincreases the volume of the zone so that the sparks, whilst continuingto strike between the electrodes, are bowed in the downstream directionbeyond the electrode extremities. Furthermore, when the air or other gasis made to gyrate or whirl in the annular gap between the electrodeextremities, the sparks striking between the electrodes are likewisegiven a whirling or gyratory movement, so that they move through theenvironmental vapourised fuel mixture to be ignited, which mixture isinvariably subject to local variations in richness.

In this connection, it should be mentioned that the electrodes aregenerally carried by ceramic components and it is known, for the purposeof cooling these ceramic components, to cause air to circulate along theigniter plug; the sparks are not affected by the airflow, the latterserving only for cooling purposes.

It will be apparent that the speed of the emergent gas or mixture shouldbe maintained at a value below the value which would extinguish thesparks, which latter value depends upon the voltage and supplyfrequency, as those skilled in the art will appreciate.

Preferably, the operative extremities of the electrodes are relativelyshaped in such a manner that the annular gap therebetween has athrottling effect on the gas or gaseous mixture passing therethroughduring use.

The means for imparting a whirling or gyratory motion to the gas orgaseous mixture may conveniently.comprise a plurality of vanes locatedin the annular passage. Alternatively, the gas or gaseous mixture may befed into the passage through an arrangement of helical grooves.

Means are preferably provided for heating the gas fed to the annularpassage, in order to facilitate ignition, for example of a jet enginewhen cold.

If desired, the plug may include a longitudinal bore in the innerelectrode for injection of fuel therethrough during use, and passagemeans for diverting a portion of said fuel for mixture with the gas fedto the annular passage.

In accordance With a further feature of the invention, a high tensionigniter plug comprises an inner electrode, an outer electrodesurrounding the inner electrode to de fine an annular passage,therebetween, said electrodes having operative extremities relativelypositioned for development of ignition sparks or arcs therebetweenduring use, and throttle means for a gas or gas/vapour mixture which inuse is fed to the annular passage for emergence through the annular gapbetween the operative extremities of the electrodes, said throttle meanscomprising an outwardly flaring generally conical deflector forming partof or carried by the operative extremity of the inner electrode. Thisdeflector either may be used in combination with the means for impartinga whirling or gyratory motion to the gas or gaseous mixture or may beused independently of this latter means. The deflector creates, in theflow of gas or gaseous mixture emerging from the annular passage, abackwash zone which promotes the formation of an ignition flame in theenvironmental vapourised fuel mixture on contact with the sparks.

If the means for imparting a whirling or gyratory motion to the air isused in combination with the deflector, then the environmentalvapourised fuel mixture is ignited by the rotating elongated sparks andan ignition flame develops in the backwash zone shielded by thedeflector.

The invention may be carried into practice in various ways, but somepractical embodiments of high tension igniter plug according theretowill now be described by way of example with reference to theaccompanying drawings, in which:

FIG. 1 schematically illustrates the basic elements of an igniter plugin accordance with the invention, viewed in axial section;

FIGS. 1a, 1b and 1c are end views of said plug, illustrating thedistribution of the sparks at various air speed values;

FIG. 1d is a schematic view similar to that of FIG. 1, showing amodification;

FIG. 2 illustrates a practical embodiment of igniter plug in accordancewith the invention, considered in section on the line II-II of FIG. 3;

FIG. 3 is a sectional view on the line III-III of FIG. 2;

FIG. 4 is a sectional view of the line IVIV of FIG. 2;

FIG. 4a is a view similar to that of FIG. 4, showing a variantembodiment;

FIG. 5 is a view similar to that of FIG. 2, showing another embodiment;

FIG. 6 is a longitudinal half-section through part of a jet enginecombustion chamber incorporating an igniter plug similar to thatillustrated in FIG. 5; and

FIG. 7 is a view similiar to those of FIGS. 2 and 5, showing anotherembodiment.

The igniter plug schematically illustrated in FIG. 1 has an innerelectrode constituted by a rod a carrying, at its operative end, aconical deflector b. The rod a is supported by a ceramic component d onthe axis of an outer cylindrical electrode c. The electrodes aresupplied in the conventional way from a high voltage supply and air isblown through the annular passage defined between the electrodes in thedirection of the arrows f.

If air is not blown through the annular passage, or if the air flows inthe direction of the arrow 1 at a negligible velocity, when a spark ewill be struck in a straight line between the electrodes (FIG. 111)along the shortest possible path.

As soon as air is blown through the passage at an appreciable speed(FIG. lb), the spark e divides into several individual sparks e,provided that the respective end rims of the outer electrode c anddeflector b form substantially coaxial circles, and the individualsparks e bow outwards in the downstream direction. If the speed of theair is increased, the sparks divide again and bow further out alongpaths of increased length. It will thus be seen, in FIG. lc, that whenthe speed of the air at the exit from the annular passage reaches apredetermined level, for example of from 4 to 5 metres per second, alarge number of sparks e", distributed around the deflector b, areproduced, forming a projecting annular bead of sparks (FIG. 1). When,moreover, the air is made to whirl in the annular passage, the sparksare individually caused to execute a rotational movement about the axisof the plug.

FIG. 1 also illustrates the advantages of the deflector in accordancewith the invention. The flow of air passing between the electrodescreates, in the slipstream of the deflector b, a backwash zone g(FIG. 1) in which develops the flame produced when the sparks contactwith the vapourised fuel mixture present at h. The use of the deflectoralso has the advantage, since it throttles the annular passage in theregion of the sparking zone, of increasing the air speed at this point;this produces a further multiplication and extension of the sparks andcreates the substantially stationary volume g where the flame canestablish itself.

In FIG. 1d, the deflector b extends in the longitudinal directionoutwardly beyond the outer electrode c so that the free edge b of thedeflector is situated beyond the free edge c of the outer electrode inthis longitudinal direction. The air deflected by the deflector exitsthrough the annular gap 1' between the free edges b and c carrying withit the sparks, which thus extend and curve to occupy an annular volume ewhich projects radially outward substantially beyond the outerelectrode. When the air in the annular passage is made to rotate, thesparks are likewise made to rotate and sweep through the whole of thevolume e As this volume 6 is larger than the volume swept by the sparksin the arrangement of FIG. 1, the sparks ignite the environmentalvapourised fuel mixture more rapidly. As in the arrangement of FIG. 1,the deflector b promotes the initial development of the flame bycreating a static backwash zone behind it.

In FIG. 1d, the deflector b is not of straight conical form, as shown inFIG. 1, but presents a concave surface to the emergent air, thereby toguide the air radially outwards.

FIGS. 2 to 4 illustrate a practical embodiment of igniter plug havingair-heating and fuel-injection facilities.

In this embodiment the annular passage between the electrodes passes aflow of air to which has been imparted a whirling or gyratory component.In the embodiment of FIG. 4a, the annular passage passes a purely axialflow of air.

The igniter plug incorporates a metal body which has a head 1 and askirt portion 2. The head 1 is in the form of a cylindrical blockcarrying two bosses 3, 4, respectively adapted to receive componentsproviding heater current supply and components providing high tensionsupply. The head is recessed at two different diameters 5 and 6. Theskirt 2 is in the form of a hollow cylinder provided at one end with aflat flange 7 adapted to be fixed to the adjacent face of the head 1using countersunk screws 1'. The flange 7 carries a boss 8 containing afuel-injection passage 9, the purpose of which will be explainedhereinafter. The flange is also provided with holes 2' for use in theassembly of the igniter plug in a jet engine combustion chamber as willbe explained hereinafter with reference to FIG. 6.

The plug has an inner electrode 10 in the form of a rod providedexternally with a conical shoulder 11 at one end and a threaded portion12 at the other, and carries externally a sealing collar 13 and a boss14. The boss 14 in fact comprises a plurality of inclined vanes 20 (FIG.4) or axially directed vanes 20a (FIG. 4a). The electrode rod 10contains a longitudinal bore 15 opening at the operative end of theelectrode into a conical shoulder 11 through a threaded hole whichreceives a fuel atomiser 16. The remote end of the bore 15 communicatesthrough radial holes in the electrode 17 with an annular peripheralthroat 18. Other radial holes 19 in the electrode 10, also leading fromthe passage 15, open on to the electrode periphery in the region of theboss 14, between the blades 20 (FIG. 4) or 20a (FIG. 4a).

The inner electrode 10 is carried by an insulating ceramic component 21of cylindrical external form, which is located in the recess 5 of themetal head 1 and abuts the base of said recess. The end portion of theelectrode 10, i.e. the end portion remote from its operative end, islocated in a central bore 22 of said component 21 and a nut 23, screwedon the thread 12, locks the collar 13 against the component 21. Thelatter component contains a radial passage 24 which, in the assembledposition, opens at one end into the annular throat 18 and at the otherinto the base of a threaded hole 25 in the metal head 1, in order tocommunicate with the passage 9 through a small pipe 26 passing through aseal 27 clamped in position by a ring 28 which is screwed into thethreaded hole 25. The component 21 contains a cavity 29 of which theperipheral wall 30 contains a hole 31 for the high tension input, and acavity 32 of the same diameter as the recess 6 in the metal head 1. Aceramic plug 33, containing a recess 34 for the nut 23, fits into thecavity 32 and the recess 6, flush with the face of the metal head 1,being secured in position by a cover 35 which is in turn fixed inposition by screws 36.

The igniter plug has an outer electrode 37 in the form of a hollowcylindrical element externally carrying, near to one of its ends, aprojection 38 which abuts against an internal circular shoulder 39formed at the end of the skirt 2 of the plug body. The other end of theelectrode 37 is force-fitted over an insulating ceramic carrier 40. Thelatter contains a cylindrical bore 41 in which engages the boss 14, i.e.the blades 20 or 20a, carried by the inner electrode. The ceramiccarrier 40 is also formed with an external annular projection 42interrupted by wide grooves 43, which projection fits inside the recess5 of the metal head 1 and abuts the peripheral wall 30 of the cavity 29in the ceramic component 21. An electrical resistor 44, wound around thecarrier 40 between the grooved collar 42 and the electrode 37, isconnected with the heating current conductors 45 which pass through theprojection 42 and the boss 3 of the metal head 1, terminating in aconventional electrical adaptor 46 screwed into said boss.

with the internal electrode 10 and its earth terminal is in contact withthe metal head 1. The high tension source, which has not been shown,should be capable of producing sparks which are sufiiciently strong andof suitable frequency to ignite a vapourised fuel mixture. The hightension current source, as well as the adaptor 47, can be ofconventional kind.

The ceramic component 21 is maintained in contact with the base of therecess and with the plug 33 by the grooved projection 42 of the ceramiccarrier 40 which is fixed to the electrode 37, the shoulder 39 of theskirt 2 bearing against the projection 38 of said electrode when theflange 7 is clamped against the head 1 by the screws 1'. The variouscomponents of the igniter plug are thus firmly held in position, theouter electrode being in electrical contact with the earth terminal ofthe electrical adaptor 47 through the intermediaries of the skirt 2 andthe head 1, and the inner electrode 10 being maintained in electricalcontact with the terminal 48. The ceramic components 21 and 40 provideelectrical insulation between the igniter plug and the resistor 44.Moreover, the ceramic component 40 co-operates with the straight orinclined vanes of the boss 14 in order to centre the inner electrode 10.

The igniter plug is supplied with compressed air through an orifice 49in the skirt 2. The air thus enters the annular space 50 defined betweenthe skirt 2 and the electrode 37, in which space it is heated by theresistor 44 when current is supplied to the latter, and passes from saidspace 50 into the cavity 29 through the grooves 43 in the projection 42of the carrier 40. The heated air then passes from said cavity 29 intothe bore 41 of the carrier 40, between the vanes 20 (FIG. 4) whichimpart a whirling or gyratory motion as it passes along the annularpassage between the inner electrode 10 and the outer electrode 37 andthence around the deflector 11. In the modification of FIG. 4a, thevanes 20a serve to guide the air in the axial direction only.

The deflector 11, located at the operative end of the plug, creates astatic zone which promotes ignition.

A supply of the fuel takes place through the passage 9. In theembodiment illustrated, this is open at both ends so as to be capable ofbeing supplied at either end, this by closing off one end and connectingthe other end to a pressurised fuel source after fitting a filter. Thepressurised fuel flows through the passage 9 into the passage 15, thencethrough the pipe 26, the passage 24, the throat 18 and the holes 17 intothe bore in the inner electrode. A portion of the fuel is injectedthrough the holes 19 and slightly enriches the air at the level of thevanes 20 or 20 formed by the boss 14, the fuel enriching the air morecompletely downstream of the deflector 11, where it is atomised by theatomiser 16.

When the igniter plug is supplied with high tension current through theadaptor 47, sparking develops in the annular gap between the edge of thedeflector 11 and the outer electrode 37. The sparks are distributedaround this annular gap and bow outwardly therefrom, in the mannerpreviously described with reference to FIG. 1. In the modification ofFIG. 4a, the sparks are stationary in position, but in the embodiment ofFIG. 4 the sparks have a rotary movement around the annular gap,sweepskirt portion penetrating inside the flame tube of the combustionchamber. Consequently, assuming that the frequency of the supply currentis sufficiently high, an annular bead of sparks is produced whichconsiderably increases the available ignition volume, as mentionedabove. The flame develops downstream of the deflector 11, fed by theatomiser 16, and then propagates itself through the flame tube, which issupplied with air and fuel in a conventional manner.

The heating of the air is not essential to the ignition function of theplug and it is within the scope of the invention to omit the resistor44. Further, the injection of fuel for ignition, through the plugitself, can be omitted if desired. Thus, we have observed, in the courseof trials using the plug, that an entirely separate combustion chamberinjector for injecting fuel into contact with the operative end of theigniter plug may, in some circumstances, suflice on its own for thesupply of fuel. However, it is necessary for efliciency that the sparksshould not develop too far from the point of injection of the fuel andthat the arcing volume should be relatively shielded from the airflowsinvariably present in the combustion chamber due to the supply ofprimary and secondary air.

FIGS. 5 and 7 respectively illustrate, by way of example, an igniterplug similar to that of FIGS. 2 and 4 or 4a but without anyfuel-injection facility, and an igniter plug without any fuel-injectionor air-heating facility. These igniter plugs operate in a similar mannerto that of FIGS. 2. to 4 or that of FIG. 4a. Those elements whichperform the same functions as corresponding elements in these earlierfigures are given the same references, but with the addition of indicesa and b in FIGS. 5 and 7 respectively.

In FIG. 5, the inner electrode 10a and its ceramic carrier 21a aresimplified due to omission of the fuelinjection facility. The full line52 schematically indicates the boundary of the backwash zone created inthe wake of the deflector 11, and the broken-line 53 indicates theannular bead formed by the sparks. The elements of the embodiment ofFIG. 7 are even simpler in design due to omission of the air-heatingfacility as well as the fuelinjection facility.

FIG. 6 shows the assembly of an igniter plug generally similar to thatof FIG. 5 in a jet engine combustion chamber. The combustion chamber isof a well known type and, for this reason, is not described in detail.It is of an annular form and comprises an annular casing 54, an annularflame tube 55 having two walls 55a and 55b welded at their forward zonesto a burner ring 550 containing orifices (not shown) adapted for theintroduction of primary air, the latter being schematically indicated inthe drawing by the arrows 58. The burners 56 are welded in positionaround the peripheries of these orifices. FIG. 6 is a longitudinalhalf-section on the axis (not shown) of the annular combustion chamber,said axis being situated beyond the drawing, the half-section beingtaken between two neighbouring burners 56.

Each burner 56 comprises an operational fuel-injector (not shown)located on its axis 57. The reference 56' indicates the fixing of theburner ring 55c to the arms of the intake casing (not shown) of thecombustion chamber. Secondary air, indicated schematically by the arrows59, circulates -between the casing 54 and the flame tube 55.

Igniter plugs are located in predetermined positions between consecutiveburners and slightly downstream of the burners. These predeterminedpositions, conveniently distributed in order to promote the propagationof the flame from one burner to the next, normally number two betweenconsecutive burners, but a larger number of igniter plugs can be used ifrequired. Each igniter plug 60 has a heating resistor but nofuel-injection facility. However, the embodiment of the igniter plugshown at 60 is constructionally slightly different from that of FIG. andin particular the high voltage supply adaptor (invisible) is directedperpendicularly to the heater current adaptor 47c secured in the boss 3cand connected to the heater resistor 44c. The other elements of theigniter plug 60, which perform the same function as correspondingelements in the embodiment of FIG. 5, are designated by the samereferences but carry the index c.

The igniter plug 60 is secured in a boss 61 in the casing 54 by means ofscrews 62 engaging in the holes 3'0 in the flange 7c, the skirt beinglocated in holes 63, 64 formed opposite one another in the casing 54 andthe external wall 55a of the flame tube, respectively. The skirt 2creaches slightly inside the flame tube and the orifice 490, locatedbetween the flame tube and the casing 54, is directed upstream in orderto be supplied directly with secondary air 59.

In the combustion chamber of FIG. 6, the annular head of sparks must becarefully localised. The high speed of the primary air 58 separating theigniter plug from the zone in which the fuel in injected by the fuelinjectors (not shown) at the centre of the burners 56 necessitatessubstantially instantaneous relaying of ignition. This is ensured byignition injectors 65 each located upstream of an igniter plug 60 andcomprising an atomiser 66 which atomises ignition fuel in the downstreamdirection, and an atomiser 67 which atomises ignition fuel forcounterfiow. In traversing the zone in which the primary air is enrichedand which is shielded by the arms of the burners, the flame developingat the igniter plug is rapidly transmitted to the zone of mixing at theinjector 65.

It will be apparent that various modifications of the above-describedembodiments are possible within the scope of the invention, as definedby the appended claims. For example, in the embodiments using inclinedvanes 20 to impart a whirling or gyratory motion to the air in theannular passage, the deflector located at the extremity of the innerelectrode 10 may be modified or even dispensed with, in part dependenton the high tension supply system used. Obviously, the dimensioning ofthe igniter plugs described may be modified. The high tensionspark-generating current may be produced using a low frequency highsupply voltage or a high frequency high supply voltage.

Although the above described assembly of an igniter plug is'concernedwith a jet engine combustion chamber, the igniter plugs of the inventioncan be used for many other applications, for instance for the ignitionof a jet engine afterburner.

We claim:

1. A high tension igniter plug, comprising:

a plug body,

an inner electrode insulatingly mounted on the plug body,

an outer electrode,

an insulating component mounting the outer electrode on the plug body tosurround the inner electrode and to define an annular passagetherebetween, the said electrodes having operative extremitiesrelatively positioned for development of spark arcs therebetween, sleevemounted on the plug body to surround the outer electrode and itssupporting component in spaced relationship thereto, said sleeve havingan aperture for gas supply, passage means in the plug components forfeeding gas from the space between the said sleeve and the said outerelectrode to the annular passage between the electrodes,

and an electrical heating element for heating said gas mounted in thespace between the said sleeve and said outer electrode on the insulatingcomponent supporting said outer electrode.

2. A high tension igniter plug, comprising:

a plug body,

an inner electrode insulatingly mounted on the plug body,

an outer electrode mounted on the plug body to surround the innerelectrode and to define an annular passage therebetween, the saidelectrodes having operative extremities relatively positioned fordevelopment of spark arcs therebetween,

a high tension connector mounted in the plug body and having respectiveelectrical connections to the two electrodes,

passage means through the plug components to supply gas to the annularpassage for emergence through the annular gap between the operativeextremities of the electrodes,

passage means in the inner electrode for fuel injection,

branch passage means for diverting a part of said fuel into the air flowin the said annular passage,

and means in the passage for imparting a directional movement to thegas/fuel mixture thus produced.

3. A high tension igniter plug according to claim 2, in

which the said means for imparting a directional movement to thegas/fuel mixture comprises a plurality of shielded conical backwash zoneon the remote side of the deflector.

5. A high tension igniter plug, comprising:

a plug body,

an inner electrode insulatingly mounted on the plug body,

an outer electrode mounted on the plug body to surround the innerelectrode and to define an annular passage therebetween, the saidelectrodes having operative extremities relatively positioned fordevelopment of spark arcs therebetween,

a high tension connector mounted in the plug body and having respectiveelectrical connections to the two electrodes,

passage means through the plug components to supply gas to the annularpassage for emergence through the annular gap between the operativeextremities of the electrodes,

and an outwardly flaring generally conical deflector forming theoperative extremity of the inner electrode, at least a part of saiddeflector extending in the longitudinal direction beyond the operativeextremity of said outer electrode.

6. A high tension igniter plug according to claim 5, in which thedeflector presents a concavely curved surface to the gas which emergesduring use from the annular passage.

7. A high tension igniter plug, comprising:

a plug body,

an inner electrode insulatingly mounted on the plug body and ending witha generally circular continuous operative extremity,

an outer electrode mounted on the plug body to surround the innerelectrode and to define an annular passage therebetween, said outerelectrode ending with a generally circular continuous operativeextremity adjacent the operative extremity of said inner electrode todefine therewith a continuous annular spark gap positioned endwise ofsaid annular passage and forming a throat constriction thereof,

a high tension connector mounted in the plug body and having respectiveelectrical connections to the two electrodes,

a passage means through the plug components to supply gas to the annularpassage for emergence through the annular spark gap between theoperative extremities of the electrodes,

and means for imparting a whirling motion about the plug axis to the gasflowing through and out of the annular passage.

References Cited UNITED STATES PATENTS 2,865,441 12/1958 Coupe 431-266XEDWARD G. FAVORS, Primary Examiner US. Cl. X.R.

